National study of US emergency department visits for acute allergic reactions, 1993 to 2004

Background: The clinical epidemiology of acute allergic reactions in the emergency department (ED) is uncertain. Objectives: To characterize ED visits for acute allergic reactions and to evaluate national trends in ED management. Methods: The National Hospital Ambulatory Medical Care Survey was used to identify a nationally representative sample of ED visits between 1993 and 2004. Cases with a diagnosis of acute allergic reaction were identified by International Classification of Diseases, Ninth Revision (ICD-9) codes (9950, 9951, 9952, 9953, 9956). Results: A total of 12.4 million allergy-related ED visits occurred from 1993 to 2004, representing 1.0% (95% confidence interval, 0.93%-1.10%) of all ED visits or 1.03 million ED visits per year. The number of allergy-related ED visits remained relatively stable, averaging 3.8 per 1,000 US population per year (95% confidence interval, 3.4-4.1; P for trend = .39). Although 63% of all visits were coded as urgent, only 4% required hospitalization. Anaphylaxis coding was rare (1%). ED staff prescribed medications in 87% of visits, especially histamine, blockers (62%; P for trend = .29). Increases were noted from 1993 to 2004 for corticosteroids (22% to 50%; P < .001), histamine, blockers (7% to 18%; P < .001), and inhaled beta-agonists (2% to 6%; P = .008). Epinephrine use was infrequent and declining (19% to 7%; P = .04). Conclusion: Between 1993 and 2004, significant variability has occurred in ED management of acute allergic reactions.